Disk Partition Table (Fixed disk boot record)
Offset Represents: (see format below) 01BE Partition 1 data table (16 bytes) 01CE Partition 2 data table (16 bytes) 01DE Partition 3 data table (16 bytes) 01EE Partition 4 data table (16 bytes) 01FE Signature (hex 55 AA, 2 bytes) Offset from beginning of partition data shown above: Offset Size Description 00 byte boot indicator 01 byte beginning sector head number 02 byte beginning sector (2 high bits of cylinder #) 03 byte beginning cylinder# (low order bits of cylinder #) 04 byte system indicator 05 byte ending sector head number 06 byte ending sector (2 high bits of cylinder #) 07 byte ending cylinder# (low order bits of cylinder #) 08 dword number of sectors preceding the partition 0B dword number of sectors in the partition Boot indicator (BYTE) 00 - non-bootable partition 80 - bootable partition (one partition only) System Indicator (BYTE) 00 - unknown operating system 01 - DOS with 12 bit FAT, 16 bit sector number 02 - XENIX 04 - DOS with 16 bit FAT, 16 bit sector number 05 - DOS Extended partition (DOS 3.3+) 06 - DOS 4.0 (Compaq 3.31), 32 bit sector number 51 - Ontrack extended partition 64 - Novell 75 - PCIX DB - CP/M FF - BBT Signature Hex 55AA marks the end of valid boot sector. This is also required in each of the partition boot records. Sector/Cylinder 2 bytes are combined to a word similar to INT 13: │7│6│5│4│3│2│1│0│ 1st byte (sector) │ │ └─┴─┴─┴─┴─┴── Sector offset within cylinder └─┴───────────── High order bits of cylinder # │7│6│5│4│3│2│1│0│ 2nd byte (cylinder) └─┴─┴─┴─┴─┴─┴───── Low order bits of cylinder # - all partitions begin on sector 1 head 0, except the first partition which follows the disk's master boot record and begins in sector 2 - some of this information may vary with some variants of DOS 3.2 and DOS 3.3 that use their own sectoring scheme for large disks - see INT 21,32 Disk Partition Table